The invention relates to a method for controlling an electrical system.
Frequently, complex electrical systems also involve equally complex regulation and control methods for operating the electrical system. An example of such an electrical system would be, for instance, the physical power distribution system for a vehicle that has a plurality of different electrical components that function as electrical sinks and/or electrical sources.
In modern vehicle development, the umbrella term “energy management system” is used for the monitoring and control of the time-related energy flows in the power distribution system of a vehicle. The energy management system may include a plurality of control chains and control loops, and is based on including a plurality of sensors and actuators.
For instance, U.S. Pat. No. 8,049,360 B2 describes a control method for an energy management system of a vehicle, in which during vehicle operation an intelligent device receives the energy requirement from the electrical system of the vehicle and distributes energy based on the requirements.
It is the object of the invention to provide an improved method for controlling such an electrical system.
This and other objects are achieved using a method according to the invention, wherein (a) a first characteristic value of the electrical system is determined; (b) for the first characteristic value, a suitable first group of optimizing variables is determined; (c) for the first group of optimizing variables, a suitable first group of command variables is determined; (d) for the first group of command variables, a first group of current boundary values is determined; (e) for each boundary value of the first group of current boundary values, a prediction is made to obtain a first group of predicted boundary values; (f) a probability is assigned to each predicted boundary value of the first group of predicted boundary values to obtain a first group of predicted, probability-related boundary values; (g) all boundary values of the first group of current boundary values and of the first group of predicted, probability-related boundary values are prioritized in order to obtain prioritized boundary values; and, (h) using the prioritized boundary values, at least one control value is calculated with which the system may be controlled.
In addition, it is advantageous when, immediately after all of the boundary values of the first group of current boundary values and the first group of predicted, probability-related boundary values have been prioritized, a second characteristic value of the system is determined. A suitable second group of optimizing variables for the second characteristic value is then determined. A second group of command variables that is suitable for the second group of optimizing variables is then determined. For the second group of command variables, a second group of current boundary values is determined. For each boundary value of the second group of current boundary values, a prediction is made to obtain a second group of predicted boundary values. A probability is assigned to each predicted boundary value of the second group of predicted boundary values to obtain a second group of predicted, probability-related boundary values. All boundary values of the first group of current boundary values and of the first group of predicted, probability-related boundary values are prioritized and all boundary values of the second group of current boundary values and of the second group of predicted probability-based boundary values are prioritized in order to obtain prioritized boundary values. Using the prioritized boundary values, at least one control value is calculated with which the system may be controlled.
In accordance with another embodiment of the invention, the method is repeated continuously.
While the electrical system is operating, the inventive method is repeated continuously to form a closed control loop and to optimize the characteristic value or values.
It is particularly advantageous when: (a) a vehicle includes the electrical system; (b) the electrical system includes an electrical power distribution system; (c) the electrical power distribution system includes a plurality of controllable electrical energy sinks; (d) the electrical power distribution system includes a plurality of controllable electrical energy sources; (e) the electrical system includes an electronic data system with which information internal to the vehicle and external to the vehicle may be ascertained; (f) an electrical energy management system controls a plurality of controllable electrical energy sinks and controls a plurality of controllable electrical energy sources; and (g) the method according to the invention is practiced by the electrical energy management system.
In accordance with a special embodiment of the invention, information internal to the vehicle and information external to the vehicle is evaluated for predicting a boundary value.
Consequently, the energy management system of the vehicle is expanded to become a predictive energy management system. Information available in the vehicle is used for predicting boundary values. The boundary values to be expected are input into the control method and influence the control value. In this manner, it is not just one actual state of one or more characteristic values of the electrical system that acts as an observation value, but also an influence that is to be expected on this one or more characteristic values. In this manner the time-related voltage stability of the power distribution system of a vehicle may be significantly improved, for instance.
The invention is based on the considerations set forth in the following: the design of the management of an electrical system, for instance the electrical power distribution system of a vehicle, occurs statically with a functionally implemented operation strategy. This is described for instance in Elektronik Automotive, October 2008. Even the coupling with navigation data is shown in various protective rights applications and publications.
However, due to the static design, it is not possible for there to be flexible reactions to some conflicting boundary values and, in these cases, the electrical power distribution system does not have optimal stability.
The method therefor determines, for different stabilization alignments for characteristic values, which act on an identical or similar command variable in their primary control action. The characteristic values have different boundary values from the system itself and from the environment of the system. In addition to optimizing the command variables relative to the specific characteristic value, the characteristic values and the specific optimization connected thereto are prioritized in a higher monitor. The resulting, comprehensively optimal command variable is determined as a function of the prioritization that is determined in this manner and that is based on system boundary values.
The sequence of steps in the optimization process includes:
1. Determine data for optimizing characteristic value 1,
2. Calculate the optimal command variable relative to characteristic value 1,
3. Perform steps 1 and 2 for additional characteristic values,
4. Determine the boundary values with the associated probabilities,
5. Prioritize the boundary values,
6. Calculate the comprehensively optimal command variable,
7. Initiate the correcting variable for adjusting the optimal command variable,
8. Repeat steps 1-7
An example of an electric system is the electric power distribution system of a motor vehicle, in which the goal is to optimize according to essentially the four following characteristic values: efficiency, provision of power, energy flow, and energy storage.
For instance, efficiency with respect to the optimal electrical system voltage is determined from the specific information regarding efficiency over the current electrical system voltage. The data are stored either centrally in a management system or in a decentralized manner in the individual components of the electrical system. In the latter case the data must be transferred to the management system.
Provision of power influences the electrical system voltage in that adequate voltage must be provided to the components in case one consumer requires high power for a brief period or a generator generates high power for a brief period. The focus here is the peak power of the components; in the first case there is a risk that an undervoltage will occur, and in the second case there is a danger that an overvoltage will occur.
In the case of energy flow, the electrical system voltage should be adjusted such that all components that are present and activated are adequately supplied with energy, and thus on average the energy storage unit, if there is one, is not discharged or overcharged. In the electrical systems in question, using the Kirchhoff equations, which are known to one skilled in the art, the electrical system voltage correlates to the energy flow equilibrium between the components.
With the energy storage unit, normally a 12-volt lead acid battery, it is important from the perspective of aging to, on the one hand, control the energy flow into and out of the storage unit for draining and overcharging and, on the other hand, keep the total energy quantity, which is determined by charging and discharging (often called cycling in this context) within limits.
The electrical system voltage together with the chemical properties of the battery determines whether the battery is being charged or discharged. A suitable or (ideally) optimal electrical system voltage is set depending on whether a peak power event is expected, whether equilibrium must be maintained in the electrical system, whether the energy storage unit requires a limit, and whether the optimum efficiency can be adjusted.
Thus, optimization is provided taking into account the prevailing boundary values, which are calculated or estimated from the electrical power distribution system itself and from the information determined from coupling to the environment.
This method attains an improvement in the stability of the electrical system, in this case of the power distribution system of a vehicle, for the purpose of improving the quality of the system and components. Likewise, the energy efficiency is improved with cost-optimized components without a separate power control in the electrical power distribution system. In addition, in a modern vehicle, the method represents a cost-effective method for improvement using available infrastructure.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawing.